This invention relates to clamping electrodes for use in a flashless D.C. butt welding method. According to the method, two ends to be butt welded are softened, by resistance heating, and plunged together. Two opposed clamping electrodes, according to the invention, are specially configured and find particular utility in the butt welding of aluminum and like metals.
Heretofore, continuous bands or hoops of aluminum alloy have been produced by a flash butt welding technique applied to the opposed ends of bar stock that has been rolled into a hoop shape. In this process, each end of a rolled piece of bar stock is clamped between a pair of clamping electrodes, the ends are positioned so that there is a small air gap between them, a charge is applied to one of the two pairs of clamping electrodes to cause an arc between the ends of the stock and the ends are plunged together to produce a weld from which a fair amount of stock metal is upset.
The opposed clamping electrodes used in the flash butt welding of aluminum alloy bar stock comprise flat major clamping surfaces adapted to engage opposed major surfaces of the stock. This process, referred to in U.S. Pat. No. 4,185,370, produces excellent welds, as evidenced by the fact that the welds stand up to the subsequent roll forming techniques described in the patent. Nonetheless, flashless welding techniques, generally, offer some advantages over flash butt welding techniques. Specifically, flashless welding consumes less metal and less electrical energy, per weld. Moreover, flashless welding is cleaner in that it produces virtually no smoke.
Flashless butt welding techniques have been successfully applied to opposed ends of steel bar stock that has been rolled into a hoop. In this process, two ends of steel bar stock are brought into contact, heated by resistance heating until they are softened, and plunged together. The clamping electrodes that have been employed in the flashless D.C. butt welding of steel correspond with the electrodes discussed above with reference to the flash butt welding of aluminum. These clamping electrodes, which are illustrated in the drawings hereof, have been found to produce unsatisfactory welds in the flashless D.C. butt welding of aluminum alloy. The difficulties which arise from attempts to employ these known electrodes in the flashless D.C. butt welding of aluminum are discussed herein.